Thermal relay



March 15, 1927.

H. D. MATTHEWS THERMAL RELAY Filed Jan. 16. 1924 WITN ESSES: g3

INVENTOR ATII'ORNEY Howard D. Mafihews.

Patented Mar. 15, 1927.

UNETED STATES PATENT OFFICE.

HOWARD D. MATTHEWS, OF EDGEWOOD, PENNSYLVANIA. ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

THERMAL RELAY.

Application filed January 16, 1924. Serial No. 686,691.

My invention relates to electrical protective devices and particularly to thermal rclays.

One object of my invention is to provide. a thermal relay that shall have such a time interval in the operation thereof as to afford protection to electrical apparatus against continued overloads.

Another object of my invention is to provide a thermal relay, of the cartridge type and of the above-indicated character, that shall have means whereby its contact members are quickly actuated in both the opening and closing operations under predetermined conditions.

A further object of my invention is to provide a thermal relay, of the above-indicated character, that shall be compact in form, relatively inexpensive to construct and reliable and effective in its operation.

My invention comprises, in general, an enclosed cylindrical casing with connecting ferrules at the ends thereof. A base member that is operatively connected between the ferrules supports a bimetallic member and an insulated terminal member. The terminal member supports a resilient contact member that is adapted to engage a movable contact member under predetermined conditions.

The movable contact member is so mounted as to be actuated with a snap action either toward or away from the resilient contact member by the bimetallic member co-operating with a system of springs. The movable contact member is surrounded by an insulating bushing that is so mounted as to preclude engagement of the two contact members when the movable contact member moves to one end of its path of movement.

In the accompanying drawings:

Figure 1 is a side view, partially in elevation and partially in section, of a thermal relay embodying my invention.

Fig. 2 is a view, partially in plan and partially in section, of the relay shown in Fig. 1.

Fig.3 is a sectional end view of the same rela- Fig. 4 is a diagrammatic view of electric circuits inwhich the relay invention may be used; and,

embodying my Fig. 5 is a side view, partially in elevation and partially in section, of an alternative method of mounting the movable contact member in the relay ventipn, and

Fig. 6 is a. partial sectional view taken on the line VI-VI of Fig. 1. Referring to Figs. 1, 2 and 3 of the drawing, a cylindrical casing 1 supports a ferrule 2 at one end and a ferrule 3 at the other end thereof. A base member 4 is rigidly secured to the ferrule 3 and supports abimetallic member 5 by means of a screw 5 and an insulating bushing 5". The base member 4 and the bimetallic member 5 are further supported by a bracket member 6 that is rigidly secured to the ferrule 2. V

The base member 4 supports a terminal member 7 by means of a screw 7 but is elecembodying my intrically insulated therefrom. One end of i supports a terminal screw 9. The other end of the terminal member supports a resilient contact member 10 that is ,biased toward the base member 4 and engages a movable contact member 11 when the free end of the bimetallic member 5 is relatively close to the base member 4.

' The contact member 11 is attached to one end of a pin 12 that is slidably mounted in an enclosing metallic bushing 13. The bushing13 is adjustably mounted on an extending member 14 that is rigidly fastened to the free end of the bimetallic member 5. The end of the pin 12 that is opposite to the end supporting the contact member 11 is provided with a groove 15 for receiving one end of each of the flat springs 16 and 17. The opposite ends of these springs engage slots in a pair of supporting members 18 and 19, respectively, that are rigidly mounted on the base member 4.

, A longitudinal slot 20 extending from one end thereof divides the bimetallic member 5 into two parts 21 and 22. The part-22 is electrically connected to the bracket member 6 but is insulated from the base member 4 b an insulating member 23. The part 21 s similarly connected to the base member 4 and insulated from the bracket member 6 My an insulating plate 23 (see F 1g. 6

' p 13 is precluded.

Thus a circuit is established from the ferrule 2 to the ferrule 3 through the bracket member 6, parts 22 and 21, respectively,- of

the bimetallic member 5, and the base member 4. -VVhen sufficient current traverses this circuit to heat the bimetallic member above a predetermined degree, its free end is moved away from the base member 4. The extending member 14 that is attached to the free end of the bimetallic member 5, thereby actuates the bushing 13 in the same direction and an annular shoulder 24 on the pin 12 causes this pin and the contact member'll that is supported thereby, to be also moved in the same direction.

If the current traversing the bimetallic member 5 is sufiicient to cause the pin 12 to be actuated, in the manner-described, until the groove 15 comes into line with the slots in the s'upportingmembers 18 and 19, the resultant force exerted by the springs 16 and 17 on the pin 12.parallel to the axis thereof becomes zero, and any further actuationv of the pin 12 in the same direction causes the springs 16 and 17 to tend to rapidly continue the actuation ofthepin 12 i1 this direction.

The pin 12 is so mounted with respect to the bushing 13 as to permit it to move freely in this direction over a certain distance. This distance is limited by a pin that extends through the bushing 13 and 'a slot 26 in the pin 12. When the pin 12 has moved to such position that the bottom of the slot 26 engages the pin 25, further actuation of the pin with respect to the bushing An insulating bushing 27 is so mounted on the metallic bushing 13 by the pin 25 that its lower edge engages the resilient contact member 10 before the pin 12 has reached the end of its path of free movement with respect to the bushing 13. The resilient contact member 10 is so biased that it tends to remain in engagement with the movable contact member 11 as the pin'12 and the contact member 11 are actuated bythe bimetallic member 5 in the manner described. When it is engaged by the lower edge of the insulating bushing 27, however, further movement of this member in thisdirection is precluded, and itis rapidly disengaged by the contact member 11 by reason of the quick actuation of the pin 12 by the springs 16 and'17.

The relay embodying my invention is adaptedto be so connected in an electrical system that disengagement of the contact. members 10 and 11 causes the circuit extending through 3 thebimetallic member 5 to be interrupted. When this circuit is interrupted, the temperature of this member decreases and the free end of the bimetallicmember moves toward its original position adjacent to the chase inember 4. i The extending member 14, the bushings 13' and, 27,

.and the pin 25 and, consequently, the bushing 27 are thereby actuated in the same d1- rectlon. I a

The pin 25, engaging the bottom of the slot 26, causes. the pin 12 and the contact.

member 11 to be also actuated in the same direction. When the pin 12 has moved so that the resultant force exerted thereon by the springs 16 and 17 tends to rapidly continue its movement in the same direction, the pin 12 and contact member 11 are given such a snap action by the springs that the contact member 11 quickly engages the contact member 10. The circuits controlled by the relay are such that when these contact members are re-engaged, the circuit extending through the bimetallic member 5 is again completed and the apparatus is in condition for operation in the same manner as previously described.

Referring to Fig. 4 of the-drawings, an electrical translating apparatus 28, to be protected, is adapted to be supplied with energy from a source 29 through a relay 30, embodying my invention, and a circuit interrupter 31. When the contact members 10 and 11 of the relay are in engagement, a circuit is completed extending from the source 29 through the ferrule 3, base member 4, supporting members 18 and 19, springs 16 and' 17, "pin 12, contact members 11 and 10, terminal member 7 and low-voltage trip coil 32 of the circuit interrupter 31, to the op posite terminal of the source 29. The coil 32 is thereby energized from the source 29 and so attracts an armature member 33 as to hold the movable member of the circuit interrupter 31 in its circuitsclosing position,

as shown in the diagram, through the toggle mechanism 34.

With the circuit interrupter 31 in its circuit-closing position, energy is supplied to theapparatus 28 from the source 29 through the relay 30 and the circuit interrupter 31. The circuit through the relay 30 traversed by this energy extends from the ferrule 3 through the base member 4, the parts 21 and 22, respectively, of the imetallic member 5, and the bracket member 6 to the ferrule 2.

exceeds a predetermined value during a predetermined interval of time, the contact members 10 and 11 are disengaged, as previouslydescribed, to interrupt the circuit extending through the trip coil 32 of the cir:

' When the current traversing this circuit cuit interrupter 31. When this coilis thus de-energiz'ed, the armature member 33 drops to permit a compression spring 35 to act upon the toggle mechanism 34inv such-mam nor as to cause the circuit interrupter 31-to.

interrupt the circuit extending to the apparatus 28.

When'the contact membersltl 11 are re .-engaged, because of the cooling of the b me elllc member 5,. the circuit through the 'modifications may be made therein, and it pended cltuims.

trip coil is re-established to hold the circuit interrupter 31 closed after it has been returned to its circuit-closing condition The system is now in the same condition as previously described and the relay 30 is in condition to again interrupt the circuit extending through the apparatus 28 should this circuit be traversed by a current in excess of the predetermined value over the predetermined interval of time.

Operation of this relay under any desired conditions within its range may be obtained by properly adjusting the position of the threaded bushing 13 with respect to the extending member 14.

Figure 5 of the drawing shows an alternative construction for the contact mechanism of the relay embodying my invention. The free end of the bimetallic member 5 supports an extending member 14 similar to that described for the preferred form of my invention. A pin 36 is adjustably mounted on the extending member 14 and is adapted to actuate a relatively movable member 37 that is rigidly attached to the pin 12. The springs 16 and 17 are mounted as before between thesupporting members 18 and 19 and the pin 12. The bimetallic member 5 now actuates the pin 12 through the extending member 14, the pin 36 and the member 37 until the springs 16 and 17 co-operate to give the pm 12 a snap action in a direction away from the resilient contact member 10. When this action takes place, engagement of the contact members 10 and His precluded because the lower end of the pin 36 engages an in sulating member 38 that is mounted on the resilient member 10.

Re-engagement of the contact members 10 and 11 in this form of my invention is effected by the actuation of the pin 12 toward the resilient member 10 from the bimetallic member 5 through the extending member 14, the pin 36 and the member 37.

This form of relay embodying my inventionmay be adjusted to operate under any desired conditions within its range by adjusting the position of the threaded pin 36 with respect to the extending member 14.

My invention is not limited to the applications illustrated nor to the structure of the relay as described above, as various ma be adapted to protect various-devices .wit out departing from the spirit and scope of the invention, asset forth in the a I cla'imfas my invention:

1. A thermal relay for electrical apparatus comprising abimetallic member, one

end of which is freely movable through a definite path, a relativel movable contact member supported by the imetallic member, a resiliently mounted contact'member which remams in engagement with the first contact definite path,

member during a certain part of its movement, and means whereby engagement of the two contact members is positively precluded when the first contact member is actuated with a-snap action.

2. A thermal relay for electrical apparatus comprising a bimetallic member, one

end of which is freely movable through a- I definite path, a relatively movable contact member supported by the bimetallic memher, a second contact member so resiliently mounted that it remains in engagement with the first contact member during a certain part of its movement, and an insulating member so mounted on said second contact member as to positively preclude engagement of the two contact members when the first contact member has traversed a certain part of its path of movement.

' 3. A thermal relay for-electrical appapoint in its path operating with the bimetallic member to actuate the pin with a snap action in either of two directions when the bimetallic member reaches certain oints in its path of movement, corresponding to definite predetermined temperatures of the bimetallic member.

5. A.- thermal relay for electrical apparatus comprising a bimetallic -member, an

adjustable bushing, a coaxial pin, and

spring means co-operating with the bimetallic member to actuate the pin with a Snap action in either of two directions, when the 'free end'of the bimetallic member reaches certainpoints on its path of vfree'movememt,

corresponding to predetermined tempera= tures of the bimetallic member.

GI. A thermal relay for electrical apparatus comprising a'bimetallic' member, one end of which is freely movable through a definite path, a relatively adjustable bushing, a relatively movable coaxial pin supporting a contact member, a resilientlymounted contact member, and spring means co-oper'ating withthe bimetallic member to cause the two contact members to disengage rapidly under predetermined conditions.

7.- A. thermalv relay for electrical .apparatus comprising a'bimetallicmember, one,

end of which is freely movable through'a definite path, a relatively adjustable bush? ing, a relatively movablecoaxial pin supporting a :contact member, a resilient y mounted contact member, and spring means co-operating with the bimetallic member to cause the two contact members to engage rapidly under predetermined conditions.

8. A thermal relay for electrical apparatus comprising a bimetallic member, one end of which is freely movable through a definite path, a relatively adjustable bushing, a relatively movable coaxial pin supporting a contactmember, a resiliently mounted contact member, and a plurality of co-operating flat springs that have a path of motion extending through a plane in which the resultant force exerted by the springs on the movable pin is zero, and that are adapted to co-operate with the bimetallic member to cause the contact members to rapidly en gage or disengage under predetermined conditions.

9. A thermal relay for electrical apparatus comprising a bimetallic member, a stationary contact member, a second contact member supported by the bimetallic member, a tog e-spring mechanism,"an'd, means whereby t e bimetallic member controls the spring mechanism to actuate the contact m'efnbers rapidly into and out of engagement.

In testimony whereof, I' have hereunto subscribed my name this 8th day of J anuary, 192 4. I I HOWARD D. MATTHEWS. 

